A crema layer, i.e. a small-bubbled foam layer, on top of coffee is a sign of a perfect cup of coffee. Such crema layer may be obtained with a high-pressure pump espresso machine only if the right grind size and right degree of tamping of the coffee are used. To make it easier to achieve the crema layer, Muttoni in U.S. Pat. No. 4,882,982, Selby in U.S. Pat. No. 5,127,318, Schiettecatte in U.S. Pat. No. 5,150,645 and Custio in EP 0682902B1 taught improved filter holders to increase the back pressure in the holder, therefore reducing the dependence of the crema layer on the grind size and degree of tamping. Unfortunately, these improved holders cause unacceptable amount of residual water above the coffee grounds, are difficult to clean and vulnerable to clogging, require very high pressure, and are complex and expensive to manufacture.
The improved holders taught by the applicant in U.S. Pat. No. 5,638,740, Akkerman-Theunisse et al. in U.S. Pat. No. 6,119,582, Brouwer in EP 1092377, and Sara Lee/DE and Philips in Senseo® coffeemakers resolved some of the above problems. These improved holders generate crema by converting coffee into a high-speed jet, forming a bath or reservoir of coffee in a container below the jet, and injecting the jet to the coffee surface in the bath or reservoir. Such improved holder, however, also has numerous drawbacks. First, it slows down the brewing process since it requires additional time to form the coffee bath in a container at the beginning of brewing and to drain the coffee bath at the end of brewing. Second, the cleaning of such improved holder is tedious since consumers have to clean both the container needed for forming the bath and the filter basket. Third, such improved holder makes all coffee drinks with the same thick crema layer, which dissatisfies those people who prefer a cup of plain coffee without a crema layer. Forth, such improved holder is still too complex and expensive for a low cost espresso machine or coffeemaker that is affordable by average consumers.
It is an object of the invention to provide a device for making crema that does not require a special container for forming a bath of coffee for the formation of crema.
It is an object of the invention to provide a device for making crema that has fewer loose parts that are in contact with coffee during brewing, therefore being easier to clean.
It is a still further object of the invention to provide a device that gives consumers a choice to make a cup of coffee drinks with or without a crema layer.
It is a still further object of the invention to provide a device for making crema that is simple and very inexpensive.
It is a still further object of the invention to provide a device for making crema that does not require additional time to build and drain a coffee bath.
It is a still further object of the invention to provide a device for making crema that does not require high pressure.
It is a still further object of the invention to provide a device for making crema that will not cause residual water above the coffee grounds.
It is a still further object of the invention to provide a device for making crema that is inexpensive enough to be disposable when it is used as part of a disposable coffee cartridge or pod.
Still other objects will become apparent after reading the accompanying drawings and description. It should be understood that the invention could still be practiced without performing one or more of the objects set forth above.